Preventive and therapeutic vaccines for human papillomavirus-associated cervical cancers

The full transcription map of cottontail rabbit papillomavirus in tumor tissues

Cottontail rabbit papillomavirus (CRPV), the first papillomavirus associated with tumor development, has been used as a powerful model to study papillomavirus pathogenesis for more than 90 years. However, lack of a comprehensive analysis of the CRPV transcriptome has impeded the understanding of CRPV biology and molecular pathogenesis. Here, we report the construction of a complete CRPV transcription map from Hershey CRPV-induced skin tumor tissues. By using RNA-seq in combination with long-reads PacBio Iso-seq, 5' and 3' RACE, primer-walking RT-PCR, Northern blot, and RNA in situ hybridization, we demonstrated that the CRPV genome transcribes its early and late RNA transcripts unidirectionally from at least five distinct major promoters (P) and polyadenylates its transcripts at two major polyadenylation (pA) sites. The viral early transcripts are primarily transcribed from three "early" promoters, P90, P156, and P907 and polyadenylated at nt 4368 by using an early polyadenylation signal (PAS) at nt 4351. Like other low-risk human papillomaviruses and animal papillomaviruses, CRPV E6 and E7 transcripts are transcribed from three separate early promoters. Transcripts from two "late" promoters, P7525, and P1225, utilize either an early PAS for E1^E4 or a late PAS at 7399 for L2 and L1 RNA polyadenylation at nt 7415 to express capsid L2 and L1 proteins respectively. By using the mapped four 5' splice sites and three 3' splice sites, CRPV RNA transcripts undergo extensive alternative splicing to produce more than 33 viral RNA isoforms for production of at least 12 viral proteins, some of which without codon optimization are expressible in rabbit RK13 and human HEK293T cells. The constructed full CRPV transcription map in this study for the first time will enhance our understanding of the structures and expressions of CRPV genes and their contribution to molecular pathogenesis and tumorigenesis.

Recent advancement of nanomedicine-based targeted delivery for cervical cancer treatment

Cervical cancer is a huge worldwide health burden, impacting women in impoverished nations in particular. Traditional therapeutic approaches, such as surgery, radiation therapy, and chemotherapy, frequently result in systemic toxicity and ineffectiveness. Nanomedicine has emerged as a viable strategy for targeted delivery of therapeutic drugs to cancer cells while decreasing off-target effects and increasing treatment success in recent years. Nanomedicine for cervical cancer introduces several novel aspects that distinguish it from previous treatment options such as tailored delivery system, precision targeting, combination therapies, real-time monitoring and diverse nanocarriers to overcome the limitations of one another. This abstract presents recent advances in nanomedicine-based tailored delivery systems for the treatment of cervical cancer. Liposomes, polymeric nanoparticles, dendrimers, and carbon nanotubes have all been intensively studied for their ability to transport chemotherapeutic medicines, nucleic acids, and imaging agents to cervical cancer cells. Because of the way these nanocarriers are designed, they may cross biological barriers and preferentially aggregate at the tumor site, boosting medicine concentration and lowering negative effects on healthy tissues. Surface modification of nanocarriers with targeting ligands like antibodies, peptides, or aptamers improves specificity for cancer cells by identifying overexpressed receptors or antigens on the tumor surface. Furthermore, nanomedicine-based techniques have made it possible to co-deliver numerous therapeutic drugs, allowing for synergistic effects and overcoming drug resistance. In preclinical and clinical investigations, combination treatments comprising chemotherapeutic medicines, gene therapy, immunotherapy, and photodynamic therapy have showed encouraging results, opening up new avenues for individualized and multimodal treatment regimens. Furthermore, the inclusion of contrast agents and imaging probes into nanocarrier systems has enabled real-time monitoring and imaging of treatment response. This enables the assessment of therapy efficacy, the early diagnosis of recurrence, and the optimization of treatment regimens.

Protection against human papillomavirus type 16-induced tumors in C57BL/6 mice by mucosal vaccination with Lactococcus lactis NZ9000 expressing E6 oncoprotein

Recombinant strains of Lactococcus lactis NZ9000 that express native and codon-optimized E6 protein (fused to the SPusp45 secretion signal) were successfully constructed by using the nisin-controlled gene expression (NICE) system. Expression of the recombinant strains was evaluated by Western blot analysis. Female mice of strain C57BL/6 were immunized orally with recombinant lactococci expressing inducible E6 oncoprotein and the antigen-specific antibody production (IgA and IgG) and cytokines were measured by ELISA and ELISPOT assay, respectively. Our outcomes indicate that the HPV-16 E6 specific IL-2- and IFN-γ-secreting lymphocytes in the antigen-stimulated intestinal mucosal lymphocytes, splenocytes and vaginal lymphocytes were significantly higher than the control groups. We showed that L. lactis having codon-optimized E6 oncogene had better inhibitory effect on tumor growth, better treatment effects on progression of tumor size, and better survival rate in comparison with L. lactis having native E6 oncogene, (P < 0.0001). In conclusion, the rE6 protein displayed by L. lactis can induce humoral and cellular immunity. Taken together, these preclinical results represent a promising step towards the development of recombinant L. lactis as a live oral vector vaccine to treat the HPV-16 associated with cervical cancer.

18F-FDG PET/CT in the evaluation of cancer cervix: Where do we stand today?

The incidence of gynecological malignancies is on the rise partly because of the availability of screening programmes, awareness, higher technological advancements, and availability of better medical care. Early diagnosis of any malignancy leads to prompt treatment. Use of 18Fluorine-Fluorodeoxyglucose (F-FDG) PET/CT in the treatment and follow-up of patients with Ca cervix considerably improves patient management. The primary diagnosis of Ca cervix is made either by biopsy of a visible tumor on the cervix or by a cone biopsy of a nonvisible malignant cervical focus. The staging procedure is purely clinical (i.e. gynecologic examination under general anesthesia) according to the International Federation of Gynaecology and Obstetrics classification. Earlier, with the nonavailability of sophisticated medical equipment and imaging specialists, oncologists relied heavily on clinical examination. However, anatomical and functional imaging has been proven to be considerably superior in understanding parametrial involvement and nodal/distant metastases in the cancer cervix than clinical examination alone. Data are evolving on the usage of F-FDG PET/CT in initial staging, treatment planning, and monitoring therapy response for gynecological malignancies. Prognostic information derived from the primary lesion such as the maximum standardized uptake value, metabolic tumor volume, and extent of para-aortic nodal metastatic disease plays a critical role in tailoring therapy on the basis of patient tumor-specific factors rather than on International Federation of Gynaecology and Obstetrics stage alone. Thus, F-FDG PET/CT needs to be listed not only under the panel of pretherapy investigations for Ca cervix but also for recurrence and therapy response assessments. It allows a more confident approach to patient management at initial staging, especially in terms of the decision to choose surgical versus palliation measures.

Therapeutic options for treatment of human papillomavirus-associated cancers - novel immunologic vaccines: ADXS11-001

Survival of patients with advanced, recurrent, or metastatic human papillomavirus (HPV)-associated cancer is suboptimal despite the availability of various treatment modalities. The recently developed bacterial vector Listeria monocytogenes (Lm) activates innate and adaptive immune responses and is expected to offer immunologic advantages. Axalimogene filolisbac (AXAL or ADXS11-001) is a novel immunotherapeutic based on the live, irreversibly attenuated Lm fused to the nonhemolytic fragment of listeriolysin O (Lm-LLO) and secretes the Lm-LLO-HPV E7 fusion protein targeting HPV-positive tumors. Herein are reported the development and recent results of various clinical trials in patients with HPV-associated cervical, head and neck, and anal cancers.

HPV vaccines: Global perspectives

The discovery of HPV as the etiological factor for HPV-associated malignancies and disease has opened up several opportunities for prevention and therapy. Current commercially available HPV vaccines (Gardasil, Gardasil 9, and Cervarix) are prophylactic in nature and derived from adjuvanted L1-based virus-like particles of HPV. Globally, through several clinical trials, they were found to be very safe and efficacious. Certain limitations such as cost-effectiveness, low coverage against all HPV types and a 3-dose schedule make these vaccines difficult to use worldwide. Approaches to address these issues involve alternate expression systems using L1 or alternate antigen (L2) as well as optimizing doses and broadening protection to provide cheap and cross-protective vaccines. Additionally, promising preclinical immunogenicity results from our own studies using alternative hosts such as Pichia and an antigen delivery system-based measles vector have potential for development as next generation HPV prophylactic vaccines. Several other therapeutic approaches are also ongoing.

Development of HPV Vaccines for HPV-associated Head and Neck Squamous Cell Carcinoma

High-risk genotypes of the human papillomavirus (HPV), particularly HPV type 16, are found in a distinct subset of head and neck squamous cell carcinomas (HNSCC). Thus, these HPV-associated HNSCC may be prevented or treated by vaccines designed to induce appropriate HPV virus-specific immune responses. Infection by HPV may be prevented by neutralizing antibodies specific for the viral capsid proteins. In clinical trials, vaccines comprised of HPV virus-like particles (VLPs) have shown great promise as prophylactic HPV vaccines. However, given that capsid proteins are not expressed at detectable levels by infected basal keratinocytes, vaccines with therapeutic potential must target other non-structural viral antigens. Two HPV oncogenic proteins, E6 and E7, are important in the induction and maintenance of cellular transformation and are co-expressed in the majority of HPV-containing carcinomas. Therefore, therapeutic vaccines targeting these proteins may have potential to control HPV-associated malignancies. Various candidate therapeutic HPV vaccines are currently being tested whereby E6 and/or E7 is administered in live vectors, in peptides or protein, in nucleic acid form, as components of chimeric VLPs, or in cell-based vaccines. Encouraging results from experimental vaccination systems in animal models have led to several prophylactic and therapeutic vaccine clinical trials. Should they fulfill their promise, these vaccines may prevent HPV infection or control its potentially life-threatening consequences in humans.

Blocking IL-10 signalling at the time of immunization renders the tumour more accessible to T cell infiltration in mice

We recently reported that blockade of IL-10 signalling at the time of a human papillomavirus (HPV) long E7 peptide/LPS immunization leads to the regression of established HPV-16 immortalized tumours in mice similar to that induced by long E7 peptide/incomplete Freund's adjuvant (IFA)-based vaccination. In this paper, we demonstrated that blockade of IL-10 signalling at the time of long E7 peptide/LPS could elicit stronger T cells responses and render the tumour more accessible for immune cell infiltration than vaccination with long E7 peptide/IFA. Furthermore, priming with long E7 peptide/LPS and IL10 signalling blockade then boosting with long E7 peptide/IFA elicits stronger CD8+ T cell responses than long E7 peptide/IFA immunization. The results suggest that priming with long E7 peptide/LPS and IL10 signalling inhibitor, then boosting with long E7 peptide/IFA elicits may lead to better HPV infection related tumour regression in clinic.

Enhancement of Ad-CRT/E7-mediated antitumor effect by preimmunization with L. lactis expressing HPV-16 E7

Although current polyvalent vaccines can prevent development of cervical cancer, they cannot be used to treat patients who already have the disease. Adenovirus expressing calreticulin-E7 (Ad-CRT-E7) has shown promising results in the cervical cancer murine model. We also demonstrated that immunization with Lactococcus lactis encoding HPV-16 E7 (Ll-E7) anchored to its surface induces significant HPV-16 E7-specific immune response. Here, we assessed the combination of both approaches in the treatment of a cervical cancer animal model. Intranasal preimmunization of Ll-E7, followed by a single Ad-CRT/E7 application, induced ∼80% of tumor suppression in comparison with controls. Mice treated with a combination of Ll-E7 and Ad-CRT/E7 resulted in a 70% survival rate 300 days post-treatment, whereas 100% of the mice in the control groups died by 50 days. Significant CD8+ cytotoxic T-lymphocytes infiltration was detected in the tumors of mice treated with Ll-E7+Ad-CRT/E7. Tumors with regression showed a greater number of positive cells for in situ TUNEL staining than controls. Our results suggest that preimmunization with Ll-E7 enhances the Ad-CRT/E7-mediated antitumor effect. This treatment provides an enormous advantage over repeated applications of Ad-CRT/E7 by maintaining the effectiveness of the three-dose application of Ad-CRT/E7, but avoiding the high systemic toxicities associated with such repeat treatments.

Oral administration of HPV-16 L2 displayed on Lactobacillus casei induces systematic and mucosal cross-neutralizing effects in Balb/c mice

The human papillomavirus (HPV) minor capsid protein, L2, is a good candidate for prophylactic vaccine development because L2-specific antibodies have cross-neutralizing activity against diverse HPV types. Here, we developed a HPV mucosal vaccine candidate using the poly-γ-glutamic acid synthetase A (pgsA) protein to display a partial HPV-16 L2 protein (N-terminal 1-224 amino acid) on the surface of Lactobacillus casei (L. casei). The oral immunization with L. casei-L2 induced productions of L2-specific serum IgG and vaginal IgG and IgA in Balb/c mice. To examine cross-neutralizing activity, we used a sensitive high-throughput neutralization assay based on HPV-16, -18, -45, -58, and bovine papillomavirus 1 (BPV1) pseudovirions. Our results revealed that mice vaccinated with L. casei-L2 not only generated neutralizing antibodies against HPV-16, but they also produced antibodies capable of cross-neutralizing the HPV-18, -45, and -58 pseudovirions. Consistent with previous reports, vaccination with HPV-16 L1 virus-like particles (VLPs) failed to show cross-neutralizing activity. Finally, we found that oral administration of L. casei-L2 induced significant neutralizing activities against genital infection by HPV-16, -18, -45, and -58 pseudovirions encoding a fluorescence reporter gene. These results collectively indicate that oral administration of L2 displayed on L. casei induces systemic and mucosal cross-neutralizing effects in mice.

The preparation of human papillomavirus type 58 vaccine and exploring its biological activity and immunogenicity in vitro

OBJECTIVES

Human papillomavirus (HPV) type 58 is the second most prevalent virus infection among Chinese women. To develop an HPV58 vaccine that combines both prophylactic and therapeutic functions, we generate a chimeric virus-like particle (cVLP).

METHODS

The cVLPs contain both whole length L1 and parts of E7 peptides either from E7 amino acids (aa) 50 to aa72 or from E7 aa4 to aa12. The HPV58 L1-E7aa50-72 and L1-E7aa4-12 fusion proteins were revealed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and confirmed by Western blot (Supplementary Digital Content 1, http://links.lww.com/IGC/A40, which shows alignment of the protein sequence between HPV58 L1-E7aa50-72/4-12 and standard sequence). Protein folding and location of cVLPs were identified by transmission electron microscope. The immunogenicity of the fusion protein was tested by enzyme-linked immunospot assay.

RESULTS

Transmission electron microscope showed that the fusion protein formed cVLPs by self-assembly and the majority of particles located in the nucleus of the sf-9 insect cells. The cVLPs displayed a strong ability to agglutinate erythrocytes, which is distinguished from the parental VLPs. In addition, the purified HPV58 L1-E7aa50-72 or L1-E7aa4-12 fusion protein induced significant numbers of interferon γ-expressing E7aa50-72- or E7aa4-12-specific CD8 T cells.

DISCUSSION

Our results indicate that the insertion of the E7aa50-72 or E7aa4-12 peptides behind L1 did not disrupt the assembly of cVLPs and provided potent immunogenicity and bioactivity, which created a powerful basis for further preparations of HPV58 vaccines with prophylactic and therapeutic effects for the treatment of HPV58-related diseases including cervical cancer.

E6 and E7 fusion immunoglobulin from human papilloma virus 16 induces dendritic cell maturation and antigen specific activation of T helper 1 response

Human papilloma virus (HPV) 16 causes cervical cancer. Induction of oncogenesis by HPV 16 is primarily dependent on the function of E6 and E7 proteins, which inactivate the function of p53 and pRB, respectively. Thus, blocking the activity of the E6 and E7 proteins from HPV 16 is critical to inhibiting oncogenesis during infection. We have expressed and purified soluble HPV 16 E6 and E7 fusion immunoglobulin (Ig), which were combined with the constant region of an Ig heavy chain, in a mammalian system. To assess whether soluble E6 and E7 fusion Igs induce effective cellular immune responses, immature dendritic cells (DCs) were treated with these fusion proteins. Soluble E6 and E7 fusion Igs effectively induced maturation of DCs. Furthermore, immunization with soluble E6 and E7 fusion Igs in mice resulted in antigen-specific activation of T helper 1 (Th1) cells. This is the first comprehensive study to show the molecular basis of how soluble HPV 16 E6 or E7 fusion Igs induces Th1 responses through the maturation of DCs. In addition, we show that DC therapy using soluble HPV E6 and E7 fusion Igs may be a valuable tool for controlling the progress of cervical cancer.

Immune responses and therapeutic antitumor effects of an experimental DNA vaccine encoding human papillomavirus type 16 oncoproteins genetically fused to herpesvirus glycoprotein D

Recombinant adenovirus or DNA vaccines encoding herpes simplex virus type 1 (HSV-1) glycoprotein D (gD) genetically fused to human papillomavirus type 16 (HPV-16) oncoproteins (E5, E6, and E7) induce antigen-specific CD8(+) T-cell responses and confer preventive resistance to transplantable murine tumor cells (TC-1 cells). In the present report, we characterized some previously uncovered aspects concerning the induction of CD8(+) T-cell responses and the therapeutic anticancer effects achieved in C57BL/6 mice immunized with pgD-E7E6E5 previously challenged with TC-1 cells. Concerning the characterization of the immune responses elicited in mice vaccinated with pgD-E7E6E5, we determined the effect of the CD4(+) T-cell requirement, longevity, and dose-dependent activation on the E7-specific CD8(+) T-cell responses. In addition, we determined the priming/boosting properties of pgD-E7E6E5 when used in combination with a recombinant serotype 68 adenovirus (AdC68) vector encoding the same chimeric antigen. Mice challenged with TC-1 cells and then immunized with three doses of pgD-E7E6E5 elicited CD8(+) T-cell responses, measured by intracellular gamma interferon (IFN-γ) and CD107a accumulation, to the three HPV-16 oncoproteins and displayed in vivo antigen-specific cytolytic activity, as demonstrated with carboxyfluorescein diacetate succinimidyl ester (CFSE)-labeled target cells pulsed with oligopeptides corresponding to the H-2D(b)-restricted immunodominant epitopes of the E7, E6, or E5 oncoprotein. Up to 70% of the mice challenged with 5 × 10(5) TC-1 cells and immunized with pgD-E7E6E5 controlled tumor development even after 3 days of tumor cell challenge. In addition, coadministration of pgD-E7E6E5 with DNA vectors encoding pGM-CSF or interleukin-12 (IL-12) enhanced the therapeutic antitumor effects for all mice challenged with TC-1 cells. In conclusion, the present results expand our previous knowledge on the immune modulation properties of the pgD-E7E6E5 vector and demonstrate, for the first time, the strong antitumor effects of the DNA vaccine, raising promising perspectives regarding the development of immunotherapeutic reagents for the control of HPV-16-associated tumors.

Human papillomavirus type 16 E6-specific antitumor immunity is induced by oral administration of HPV16 E6-expressing Lactobacillus casei in C57BL/6 mice

Given that local cell-mediated immunity (CMI) against the human papillomavirus type 16 E6 (HPV16 E6) protein is important for eradication of HPV16 E6-expressing cancer cells in the cervical mucosa, the HPV16 E6 protein may be a target for the mucosal immunotherapy of cervical cancer. Here, we expressed the HPV16 E6 antigen on Lactobacillus casei (L. casei) and investigated E6-specific CMI following oral administration of the L. casei-PgsA-E6 to mice. Surface expression of HPV16 E6 antigens was confirmed and mice were orally inoculated with the L. casei-PgsA or the L. casei-PgsA-E6. Compared to the L. casei-PgsA-treated mice, significantly higher levels of serum IgG and mucosal IgA were observed in L. casei-PgsA-E6-immunized mice; these differences were significantly enhanced after boost. Consistent with this, systemic and local CMI were significantly increased after the boost, as shown by increased counts of IFN-γ-secreting cells in splenocytes, mesenteric lymph nodes (MLN), and vaginal samples. Furthermore, in the TC-1 tumor model, animals receiving the orally administered L. casei-PgsA-E6 showed reduced tumor size and increased survival rate versus mice receiving control (L. casei-PgsA) immunization. We also found that L. casei-PgsA-E6-induced antitumor effect was decreased by in vivo depletion of CD4⁺ or CD8⁺ T cells. Collectively, these results indicate that the oral administration of lactobacilli bearing the surface-displayed E6 protein induces T cell-mediated cellular immunity and antitumor effects in mice.

Increase of human papillomavirus-16 E7-specific T helper type 1 response in peripheral blood of cervical cancer patients after radiotherapy

It has been suggested that tumour cell lysis by gamma-radiation induces a tumoral antigen release eliciting an immune response. It is not clear how a specific immune response in cervical cancer patients is developed after radiotherapy. This study is an attempt to investigate the role of the human papillomavirus type 16 (HPV-16) E7-specific T helper response before and after radiotherapy. Lymphocytes were isolated from 32 cervical cancer patients before and after radiotherapy and from 16 healthy women. They were stimulated for 12 hr with autologous HPV-16 E7-pulsed monocyte-derived dendritic cells or directly with HPV-16 E7 synthetic peptides: E7(51-70), E7(65-84) and E7(79-98). The cells were stained for CD4, CD69, intracellular interferon-gamma (IFN-gamma) and interleukin-4 (IL-4) cytokines and analysed by flow cytometry. A specific CD4(+) CD69(+) IFN-gamma(+) immune response against HPV-16 E7(79-98) peptide was observed in 10 of 14 patients (71.4%) after treatment, compared with 4 of 14 (28.5%) before radiotherapy (P = 0.039); however, this response was not associated with a successful clinical response. Before treatment, 5 of 31 patients showed a HPV-16 E7(79-98)-specific T helper type 2 (Th2) response. Interestingly, this response was significantly associated with a decrease in disease-free survival (P = 0.027). These results suggest that a Th2-type cellular response could be useful as a predictor of recurrence and poor prognosis. An increase of the HPV-specific immune response was observed after radiotherapy; however, it is not enough to control completely the disease after treatment. Our results support that the E7-specific T-cell IFN-gamma response in cervical cancer patients, rather than reflecting the host's capability of controlling tumour growth, might be an indicator for disease severity.

The role of infectious agents in the etiology of ocular adnexal neoplasia

Given the fact that infectious agents contribute to around 18% of human cancers worldwide, it would seem prudent to explore their role in neoplasms of the ocular adnexa: primary malignancies of the conjunctiva, lacrimal glands, eyelids, and orbit. By elucidating the mechanisms by which infectious agents contribute to oncogenesis, the management, treatment, and prevention of these neoplasms may one day parallel what is already in place for cancers such as cervical cancer, hepatocellular carcinoma, gastric mucosa-associated lymphoid tissue lymphoma and gastric adenocarcinoma. Antibiotic treatment and vaccines against infectious agents may herald a future with a curtailed role for traditional therapies of surgery, radiation, and chemotherapy. Unlike other malignancies for which large epidemiological studies are available, analyzing ocular adnexal neoplasms is challenging as they are relatively rare. Additionally, putative infectious agents seemingly display an immense geographic variation that has led to much debate regarding the relative importance of one organism versus another. This review discusses the pathogenetic role of several microorganisms in different ocular adnexal malignancies, including human papilloma virus in conjunctival papilloma and squamous cell carcinoma, human immunodeficiency virus in conjunctival squamous carcinoma, Kaposi sarcoma-associated herpes virus or human herpes simplex virus-8 (KSHV/HHV-8) in conjunctival Kaposi sarcoma, Helicobacter pylori (H. pylori,), Chlamydia, and hepatitis C virus in ocular adnexal mucosa-associated lymphoid tissue lymphomas. Unlike cervical cancer where a single infectious agent, human papilloma virus, is found in greater than 99% of lesions, multiple organisms may play a role in the etiology of certain ocular adnexal neoplasms by acting through similar mechanisms of oncogenesis, including chronic antigenic stimulation and the action of infectious oncogenes. However, similar to other human malignancies, ultimately the role of infectious agents in ocular adnexal neoplasms is most likely as a cofactor to genetic and environmental risk factors.

Detection of L1, infectious virions and anti-L1 antibody in domestic rabbits infected with cottontail rabbit papillomavirus

Shope papillomavirus or cottontail rabbit papillomavirus (CRPV) is one of the first small DNA tumour viruses to be characterized. Although the natural host for CRPV is the cottontail rabbit (Sylvilagus floridanus), CRPV can infect domestic laboratory rabbits (Oryctolagus cuniculus) and induce tumour outgrowth and cancer development. In previous studies, investigators attempted to passage CRPV in domestic rabbits, but achieved very limited success, leading to the suggestion that CRPV infection in domestic rabbits was abortive. The persistence of specific anti-L1 antibody in sera from rabbits infected with either virus or viral DNA led us to revisit the questions as to whether L1 and infectious CRPV can be produced in domestic rabbit tissues. We detected various levels of L1 protein in most papillomas from CRPV-infected rabbits using recently developed monoclonal antibodies. Sensitive in vitro infectivity assays additionally confirmed that extracts from these papillomas were infectious. These studies demonstrated that the CRPV/New Zealand White rabbit model could be used as an in vivo model to study natural virus infection and viral life cycle of CRPV and not be limited to studies on abortive infections.

Induction of mucosal and systemic immune responses following oral immunization of mice with Lactococcus lactis expressing human papillomavirus type 16 L1

Human papillomavirus type 16 L1 (HPV16 L1) has shown considerable promise as a parenteral vaccine for prevention of cervical cancers. Here, we report the possibility of oral vaccination for HPV16 L1 using Lactococcus lactis (L. lactis) as a live vector. L. lactis MG1363 was transformed with two types of HPV16 L1-encoding plasmids for intracellular expression or secretion. L. lactis transformed with HPV16 L1-encoding plasmids retained biochemical lactic acid production capability. The mucosal and systemic immune responses were affected by the cellular location of expressed HPV16 L1 proteins in L. lactis. Serum IgG responses were induced after oral immunizations of L. lactis secreting HPV16 L1. Vaginal IgA immune responses were observed following oral immunization with L. lactis expressing HPV16 L1 in an intracellular form, but not with L. lactis secreting HPV16 L1. Furthermore, induction of HPV16 L1-specific mucosal immune responses was affected by immunization frequency. Six immunizations over 5 weeks were required to induce vaginal immune responses. The levels of HPV16 L1-specific vaginal IgA were maintained until 12 weeks after the first vaccination. These results suggest the feasibility of L. lactis as an oral vaccine vehicle of HPV16 L1 and demonstrate the importance of cellular loci of expressed antigen for induction of vaginal and systemic immune responses.

Modified HPV16 E7/HSP70 DNA vaccine with high safety and enhanced cellular immunity represses murine lung metastatic tumors with downregulated expression of MHC class I molecules

OBJECTIVE

To explore whether the modified E7-HSP70, which has been introduced mutations in two zinc-binding motifs of E7, will eliminate its transformation potential and enhance the immunogenicity of fusion protein and repress E7 containing tumors with a low level of MHC-I molecules to lung metastatic in murine model.

METHODS

In this study, we examined the transforming properties of mutant E7 oncoprotein by the soft agar colony-formation assays, explored the immunogenicity of modified E7-HSP70 gene by various cellular and humor immune responses and evaluated the effect of treating lung metastatic tumor with a low expressing MHC-I molecules by tumor challenge assay and therapeutic experiment.

RESULTS

The mutant E7 oncoprotein has completely lost its transforming properties as measured in the soft agar colony-formation assays. Modified E7-HSP70 gene inducted stronger E7-specific cellular immune response than that induced by unmodified E7-HSP70. More importantly, the new construct significantly reduced the number of B16-HPV16E7 lung metastases.

CONCLUSION

The modified E7-HSP70 gene may be as a powerful and safe DNA vaccine in controlling the hematogenous spread of HPV16E7-associated tumors with low expression of MHC-I molecules. In addition, the B16-HPV16E7 lung metastasis model can be used to test the efficacy of various E7-specific vaccines and immunotherapeutic strategies in settings more relevant to clinical requirements.

Immunological role of dendritic cells in cervical cancer

Cervical cancer is the second most frequent gynecological malignancy in the world. Human papillomavirus (HPV) infection is the primary etiologic agent of cervical cancer. However, HPV alone is not sufficient for tumor progression. The clinical manifestation of HPV infection depends also on the host's immune status. Both innate and adaptive immunity play a role in controlling HPV infection. In untransformed HPV-infected keratinocytes, the innate immunity is induced to eliminate the invading HPV pathogen through sensitization to HPV-related proteins by epithelial-residing Langerhans cells (LCs), macrophages, and other immune cells. Once the HPV infection escapes from initial patrolling by innate immunity, cellular immunity becomes in charge of killing the HPV-infected keratinocytes of the uterine cervix through systemic immune response developing by dendritic cells (DCs) in the regional lymphoid organs or through local immune response developing by LCs in the cervix. Thereby, DC/LC plays a critical role in eliciting innate and adaptive cellular immune responses against HPV infection. HPV-associated cervical malignancies might be prevented or treated by induction of the appropriate virus-specific immune responses in patients. Encouraging results from experimental vaccination systems in animal models have led to several prophylactic and therapeutic vaccine clinical trials.

A DNA vaccine encoding a codon-optimized human papillomavirus type 16 E6 gene enhances CTL response and anti-tumor activity

The HPV oncoproteins E6 and E7 are consistently expressed in HPV-associated cancer cells and are responsible for their malignant transformation. Therefore, HPV E6 and E7 are ideal target antigens for developing vaccines and immunotherapeutic strategies against HPV-associated neoplasms. Recently, it has been demonstrated that codon optimization of the HPV-16 E7 gene resulted in highly efficient translation of E7 and increased the immunogenicity of E7-specific DNA vaccines. Since vaccines targeting E6 also represent an important strategy for controlling HPV-associated lesions, we developed a codon-optimized HPV-16 E6 DNA vaccine (pNGVL4a-E6/opt) and characterized the E6-specific CD8+ T cell immune responses as well as the protective and therapeutic anti-tumor effects in vaccinated C57BL/6 mice. Our data indicated that transfection of human embryonic kidney cells (293 cells) with pNGVL4a-E6/opt resulted in highly efficient translation of E6. In addition, vaccination with pNGVL4a-E6/opt significantly enhanced E6-specific CD8+ T cell immune responses in C57BL/6 mice. Mice vaccinated with pNGVL4a-E6/opt are able to generate potent protective and therapeutic antitumor effects against challenge with E6-expressing tumor cell line, TC-1. Thus, DNA vaccines encoding a codon-optimized HPV-16 E6 may be a promising strategy for improving the potency of prophylactic and therapeutic HPV vaccines with potential clinical implications.

Sindbis virus replicon particles encoding calreticulin linked to a tumor antigen generate long-term tumor-specific immunity

Alphavirus vectors have emerged as a promising strategy for the development of cancer vaccines and gene therapy applications. In this study, we used the replication-defective vaccine vector SIN replicon particles from a new packaging cell line (PCL) to develop SIN replicon particles encoding calreticulin (CRT) linked to a model tumor antigen, human papillomavirus type 16 (HPV16) E7 protein. The linkage of CRT to E7 in SIN replicon particles resulted in a significant increase in E7-specific CD8(+) T-cell precursors and a strong antitumor effect against E7-expressing tumors in vaccinated mice. SINrep5-CRT/E7 replicon particles enhanced presentation of E7 through the major histocompatibility complex (MHC) class I pathway by infecting dendritic cells (DCs) directly and pulsing DCs with lysates of cells infected by SINrep5-CRT/E7 replicons. Vaccination of immunocompromised (BALB/c nu/nu) mice with SINrep5-CRT/E7 replicon particles also generated significant reduction of lung tumor nodules, suggesting that antiangiogenesis may contribute to the antitumor effect of SINrep5-CRT/E7 replicon particles. Furthermore, SINrep5-CRT/E7 replicon particles generated long-term in vivo tumor protection effects and antigen-specific memory immunities. We concluded that the CRT strategy used in the context of SIN replicon particles facilitated the generation of a highly effective vaccine for cancer prophylaxis and immunotherapy.

Presence and Influence of Human Papillomaviruses (HPV) in Tonsillar Cancer

Tonsillar cancer is the most common of the oropharyngeal carcinomas and human papillomavirus (HPV) has been found to be present in approximately half of all cases. Patients with HPV-positive tonsillar cancer have been observed to have a better clinical outcome than patients with HPV-negative tonsillar cancer. Moreover, patients with tonsillar cancer and a high viral load have been shown to have a better clinical outcome, including increased survival, compared to patients with a lower HPV load in their tumors. Recent findings show that HPV-positive tumors are not more radiosensitive and do not have fewer chromosomal aberrations than HPV-negative tumors, although some chromosomal differences may exist between HPV-positive and -negative tonsillar tumors. Current experimental and clinical data indicate that an active antiviral cellular immune response may contribute to this better clinical outcome. These data are also in line with the findings that the frequency of tonsillar cancer is increased in patients with an impaired cellular immune system. Thus, therapeutic and preventive HPV-16 antiviral immune vaccination trials may be worthwhile, not only in cervical cancer, but also in tonsillar cancer.

Development of a DNA vaccine targeting human papillomavirus type 16 oncoprotein E6

Human papillomavirus (HPV), particularly type 16 (HPV-16), is present in more than 99% of cervical cancers. The HPV oncoproteins E6 and E7 are constantly expressed and therefore represent ideal targets for HPV vaccine development. We previously developed DNA vaccines encoding calreticulin (CRT) linked to HPV-16 E7 and generated potent E7-specific CD8(+) T-cell immune responses and antitumor effects against an E7-expressing tumor. Since vaccines targeting E6 also represent an important strategy for controlling HPV-associated lesions, we developed a DNA vaccine encoding CRT linked to E6 (CRT/E6). Our results indicated that the CRT/E6 DNA vaccine, but not a wild-type E6 DNA vaccine, generated significant E6-specific CD8(+) T-cell immune responses in vaccinated mice. Mapping of the immunodominant epitope of E6 revealed that an E6 peptide comprising amino acids (aa) 48 to 57 (E6 aa48-57), presented by H-2K(b), is the optimal peptide and that the region of E6 comprising aa 50 to 57 represents the minimal core sequence required for activating E6-specific CD8(+) T lymphocytes. We also demonstrated that E6 aa48-57 contains cytotoxic T-lymphocyte epitopes naturally presented by E6-expressing TC-1 cells. Vaccination with a CRT/E6 but not a CRT/mtE6 (lacking aa 50 to 57 of E6) DNA vaccine could protect vaccinated mice from challenge with E6-expressing TC-1 tumors. Thus, our data indicate that E6 aa48-57 contains the immunodominant epitope and that a CRT/E6 DNA vaccine may be useful for control of HPV infection and HPV-associated lesions.

Cervical response to vaccination against HPV16 E7 in case of severe dysplasia

OBJECTIVE

To evaluate the tolerance to vaccination against human papillomavirus (HPV)16 E7 (in SB adjuvant ASO2B) and its histological and immunohistological effects on HPV16 associated high-grade cervical dysplasias associated with HPV16.

STUDY DESIGN

Five patients with histologically demonstrated severe cervical dysplasia (CIN3) HPV16 positive were injected three times before conization was performed 2 months after the first injection. We studied cytological, histological, proliferative pattern and immune profile before and after vaccination. The slides were compared with those obtained from non-injected patients.

RESULTS

The injections were well tolerated and the specimens displayed a limited regression of the lesions. Nevertheless, massive CD4 and CD8 T cell lymphocytic infiltration was noticed after vaccination.

DISCUSSION

We conclude that the vaccination we used provides an obvious immune histological reaction in the HPV infected cervix and that the 2 months delay before the final step (conization) is done is probably too short.

Immunisation with modified HPV16 E7 genes against mouse oncogenic TC-1 cell sublines with downregulated expression of MHC class I molecules

Human papillomavirus type 16 (HPV16)-transformed mouse TC-1 cells are extensively used in the evaluation of efficacy of experimental vaccines against tumours induced by HPVs. As these cells strongly express MHC class I molecules and downregulation of MHC class I surface expression is one of the important mechanisms that enable tumour escape from the host immune system, we undertook to derive TC-1 clones with reduced expression of MHC class I antigens. TC-1 cells were inoculated into mice preimmunised with an E7 gene-based DNA vaccine and from tumours developing in a portion of the animals, cell clones with downregulated MHC class I surface expression were isolated. Treatment with IFN-gamma resulted in an upregulation of MHC class I molecules in these cells, but after IFN-gamma removal, their expression gradually dropped again. When the expression of some components of the antigen-processing machinery (APM; LMP-2, TAP-1, and TAP-2) was tested, a reduced TAP-1 production was detected in cell lines with downregulated MHC class I expression. An enhanced immunoresistance of TC-1-derived clones with reduced MHC class I expression was observed in animals immunised with plasmids carrying modified E7 genes. Apart from the previously described fusion gene Sig/E7/LAMP-1, a new construct, Sig/E7GGG/LAMP-1, with a mutated Rb-binding site, was also used for immunisation. No significant change of immunogenicity was recorded for Sig/E7GGG/LAMP-1. Cell lines with downregulated MHC class I expression derived from TC-1 cells may represent a useful model for testing therapeutic anti-HPV vaccines in settings more relevant to clinical requirements.

Cancer immunogene therapy: a review

Although immunotherapy has long held out promise as a specific, potent approach to cancer therapy, clinical applications have been unrewarding to date. However, advances in gene transfer technology and basic immunology have opened new avenues to stimulate antitumor immune responses including immunogene therapy. Many different approaches to immunogene therapy have been identified. These include transferring genes encoding proinflammatory proteins to tumor cells, suppressing immunosuppressive gene expression, and transferring proinflammatory genes and/or tumor antigen genes to professional antigen-presenting cells. In some cases, genes are transferred to tumor or antigen-presenting cells in situ. In others, gene transfer is performed ex vivo as part of preparing an anticancer vaccine. We discuss the underlying approach, relative success, and clinical application of various cancer immunogene therapy strategies, paying particular attention to immunogene therapy vaccines. Large numbers of preclinical studies have been reported, but only scattered clinical trial results have appeared in the literature. Although very successful preclinically, the ideal cancer immunogene therapy approach remains to be determined and will likely vary with tumor type. Clinical impact may be improved in the future as treatment protocols are refined.

Amino acid residues in the carboxy-terminal region of cottontail rabbit papillomavirus E6 influence spontaneous regression of cutaneous papillomas

Previous studies have identified two different strains of cottontail rabbit papillomavirus (CRPV) that differ by approximately 5% in base pair sequence and that perform quite differently when used to challenge New Zealand White (NZW) rabbit skin. One strain caused persistent lesions (progressor strain), and the other induced papillomas that spontaneously regressed (regressor strain) at high frequencies (J. Salmon, M. Nonnenmacher, S. Caze, P. Flamant, O. Croissant, G. Orth, and F. Breitburd, J. Virol. 74:10766-10777, 2000; J. Salmon, N. Ramoz, P. Cassonnet, G. Orth, and F. Breitburd, Virology 235:228-234, 1997). We generated a panel of CRPV genomes that contained chimeric and mutant progressor and regressor strain E6 genes and assessed the outcome upon infection of both outbred and EIII/JC inbred NZW rabbits. The carboxy-terminal 77-amino-acid region of the regressor CRPV strain E6, which contained 15 amino acid residues that are different from those of the equivalent region of the persistent CRPV strain E6, played a dominant role in the conversion of the persistent CRPV strain to one showing high rates of spontaneous regressions. In addition, a single amino acid change (G252E) in the E6 protein of the CRPV progressor strain led to high frequencies of spontaneous regressions in inbred rabbits. These observations imply that small changes in the amino acid sequences of papillomavirus proteins can dramatically impact the outcome of natural host immune responses to these viral infections. The data imply that intrastrain differences between separate isolates of a single papillomavirus type (such as human papillomavirus type 16) may contribute to a collective variability in host immune responses in outbred human populations.

Cancer immunotherapy using Sindbis virus replicon particles encoding a VP22-antigen fusion

Alphavirus vectors have emerged as a strategy for the development of cancer vaccines and gene therapy applications. The availability of a new packaging cell line (PCL), which is capable of generating alphavirus replicon particles without contamination from replication-competent virus, has advanced the field of vaccine development. This replication-defective vaccine vector has potential advantages over naked nucleic acid vaccines, such as increased efficiency of gene delivery and large-scale production. We have developed a new strategy to enhance nucleic acid vaccine potency by linking VP22, a herpes simplex virus type 1 (HSV-1) tegument protein, to a model antigen. This strategy facilitated the spread of linked E7 antigen to neighboring cells. In this study, we created a recombinant Sindbis virus (SIN)-based replicon particle encoding VP22 linked to a model tumor antigen, human papillomavirus type 16 (HPV-16) E7, using a stable SIN PCL. The linkage of VP22 to E7 in these SIN replicon particles resulted in a significant increase in the number of E7-specific CD8(+) T cell precursors and a strong antitumor effect against E7-expressing tumors in vaccinated C57BL/6 mice relative to wild-type E7 SIN replicon particles. Furthermore, a head-to-head comparison of VP22-E7-containing naked DNA, naked RNA replicons, or RNA replicon particle vaccines indicated that SINrep5-VP22/E7 replicon particles generated the most potent therapeutic antitumor effect. Our results indicated that the VP22 strategy used in the context of SIN replicon particles may facilitate the generation of a highly effective vaccine for widespread immunization.

Therapy for Recurrent Respiratory Papillomatosis

Human papillomaviruses types 6 or 11 are aetiological agents of recurrent respiratory papillomatosis, a disease characterized by benign exophytic tumours usually on the vocal cords. Surgery debulks the tumours, but these growths generally recur at regular intervals. Adjunct medical treatments, aimed at containing the virus and growth of tumours, include indole-3-carbinol or its dimer diindolylmethane, interferon, photodynamic therapy and others. Preventive and therapeutic vaccines hold promise for eliminating the virus.

Papillomavirus-like particle based vaccines: cervical cancer and beyond

Non-infectious human papillomavirus-like particles (VLP), composed of the L1 major capsid protein, are under active development as vaccines to prevent cervical cancer. They would presumably function primarily by generating virion-neutralising antibodies against the genital human papillomavirus (HPV) types that are the principal cause of most cervical cancers. Early phase clinical studies indicate that the VLP vaccines are well tolerated and able to consistently induce high titres of virus type-specific neutralising antibodies. Two types of second-generation VLP-based subunit vaccines with therapeutic implications, both related and unrelated to papillomavirus infection, are in preclinical development. One type seeks to induce cell-mediated immune responses, especially cytotoxic lymphocytes (CTL), against non-structural papillomavirus proteins, proteins of other viruses, or tumour associated antigens. The target antigen is incorporated into the VLPs as a fusion protein of L1 or the L2 minor capsid protein. In mouse models, this approach has generated potent CTL responses after low dose vaccination in the absence adjuvant. The second type of therapeutic VLP-based vaccine seeks to generate autoantibodies to self-antigens. The display of self polypeptides in the context of the highly ordered array of repetitive elements on the papillomavirus VLP surface abrogates the ability of the humoral immune system to functionally distinguish between foreign and self. High titre and high avidity auto-reactive IgG antibodies have been induced to both soluble (TNF-alpha) and cell surface (CCR5) central self-antigens. Vaccines based on this approach could potentially be effective alternatives to monoclonal antibody (mAb)-based therapies for a variety of disease targets.

Enhancement of Sindbis virus self-replicating RNA vaccine potency by linkage of Mycobacterium tuberculosis heat shock protein 70 gene to an antigen gene

Recently, self-replicating RNA vaccines (RNA replicons) have emerged as an effective strategy for nucleic acid vaccine development. Unlike naked DNA vaccines, RNA replicons eventually cause lysis of transfected cells and therefore do not raise the concern of integration into the host genome. We evaluated the effect of linking human papillomavirus type 16 E7 as a model Ag to Mycobacterium tuberculosis heat shock protein 70 (HSP70) on the potency of Ag-specific immunity generated by a Sindbis virus self-replicating RNA vector, SINrep5. Our results indicated that this RNA replicon vaccine containing an E7/HSP70 fusion gene generated significantly higher E7-specific T cell-mediated immune responses in vaccinated mice than did vaccines containing the wild-type E7 gene. Furthermore, our in vitro studies demonstrated that E7 Ag from E7/HSP70 RNA replicon-transfected cells can be processed by bone marrow-derived dendritic cells and presented more efficiently through the MHC class I pathway than can wild-type E7 RNA replicon-transfected cells. More importantly, the fusion of HSP70 to E7 converted a less effective vaccine into one with significant potency against E7-expressing tumors. This antitumor effect was dependent on NK cells and CD8(+) T cells. These results indicated that fusion of HSP70 to an Ag gene may greatly enhance the potency of self-replicating RNA vaccines.